We intend to study the effects of diet and physiological state on properties of enzymes which regulate pathways of glycolysis, gluconeogenesis and lipogenesis in rat liver. In particular, we propose to study the regulation of fructose-1,6-diphosphatase (FDPase), phosphofructokinase (PFK), pyruvate kinase (PK) and acetyl CoA carboxylase in rats subjected to a variety of nutritional and hormonal treatments. These treatments, which include starvation, glucagon administration, diabetes and subsequent insulin therapy, and feeding diets high in protein, fat, starch, glucose sucrose of fructose, are designed to produce metabolic responses ranging from gluconeogenesis to lipogenesis in the livers of these animals. We will determine the effects of such treatments on alterations of these enzymes by phosphorylation or by other means, (e.g., proteolytic modification of FDPase) and the effects of these alterations on the regulation of enzyme activity by known and potential allosteric effects. We intend, in particular, to examine the potential regulation of FDPase, PFK and acetyl CoA carboxylase by 6-phosphogluconate (6-PG) and to further examine the regulation of PK by 6-PG. The effects of 6-PG on the activities of purified enzymes will be determined in vitro. Furthermore, the effects of enzyme phosphorylation and regulation by 6PG will be estimated in isolated hepatocytes by determining the effects of, respectively, glucagon and 6-aminonicotinamide (which increases intracellular 6-PG) on fulx through the enzymes of interest. It is believed that 6-PG may be an important regulator of hepatic metabolism under lipogenic conditions and may contribute to the rapid formation of triglycerides from fructose.